Single well subsurface electrification process



Oct. 12, 1965 E. SARAPUU 3,211,220

SINGLE WELL SUBSURFACE ELECTRIFICATION PROCESS Filed April 17, 1961 rTORNEV.

Unite 3,211,220 PatentedOct. 1 1965 (1) where wellbores must be drilledinto a formation 3,211,220 (no old holes available), (2) when only onewellbore is SINGLE WELL g kg ELECTRKFMATION readily available reachingto the formation to be treated,

Erich Sarapuu, Kansas City, Mo., assignor to Electrofrac Corporation, acorporation of Delaware Filed Apr. 17, 1961, Ser. No. 103,429 3 Claims.(Cl. 166-39) This application is an improvement over my Patent2,795,279, below, and is a continuation-in-part of my application SerialNo. 3,897, filed January 21, 1960 Electro-Repressurization, now U.S.Patent No. 3,141,504, and my application Serial No. 41,418, filed July7, 1960, entitled Electrolinking by Impulse Voltages.

This invention relates to subsurface electrical treatment andelectrification processes such as wellbore and sand heating, ignition,electrolinking, electrocarbonization and electrofracturing and refersmore particularly to the practice of such processes in a single wellboreutilizing only one electrode or electrode array in said single wellborecommunicating therein with the formation to be electrically treated as asurface ground (a ground not communicating with the formation in whichsaid subsurface electrode is established).

My Patent 2,795,279 issued July 11, 1957, discloses a Method ofUnderground Electrolinking and Electrocarbonization of Mineral Fuelswherein high energy electric current flows between separate electrodesin separate wellbores in a single earth formation, thereby linking theelectrodes electrically and also physically by channels electricallyformed in said formation.

My application Serial No. 3,897, filed January 21, 1960, and now PatentNo. 3,141,504, for Electro-Repressurization discloses methods of andapparatus for electrically detonating and igniting explosive gas bodiespositioned in earth horizons, particularly oil sands.

My application Serial N0. 41,418, filed July 7, 1960 for Electrolinkingby Impulse Voltages discloses means of and methods for applying highvoltage impulses to subsurface gas formations whereby to so electricallylink one underground electrode to another as to make actual physicalcracks or fractures next to the wellbores con taining the electrodes.

It is well known to apply electrical current to oil horizons and othersubsurface formations to aid oil or mineral production and achievevarious related purposes therein. Thus, subsurface and formation heatingby electrical means, electrolytic migration of subsurface fluids,linking of electrodes in subsurface formations, physically linking suchelectrodes by carbonized channels, circumferential wellborecarbonization, wellbore fracturing by electrical means, etc. are alldescribed in these references. The typical complete well installationsutilized in practicing such processes contemplates spaced wellbores withelectrodes or electrode analogs embedded in a single formation or in thefluids of such single formation or yet in gravel packs communicatingwith a single formation whereby to transfer electrical energy to theformation or fluids thereof.

In most of the described applications, since it is desirable to retainas much as possible of the electrical energy within the horizon or sandor formation, this described paired wellbore and electrode completioninto the sand is the most economic and feasible. Indeed, this is all theart contemplates.

However, in certain geographic, geological and physical situations, bothsubsurface and surface and also in the interest of economy, thenecessity of utilization of drilling a plurality of closely spaced Wellscompleting them and installing complex expensive apparatus thereat ismost undesirable and impractical. Particularly this is the case (3)where underground permeability conditions are unusual or peculiar, (4)where terrain makes it impossible or overwhelmingly expensive to providewellbores spaced as would ordinarily be desirable or required and (5)where the formation to be electrically treated is extremely deep.

In any case, it can be truthfully said to be eminently desirable to beable to produce any, all or a substantial number of the benefits andoperations of multiple wellbore electrification processes at, in or witha single wellbore penetrating the horizon to be treated. Particularlythis is the case when the electrification process involved is one whichcreates effects at or adjacent to the wellbore itself, such aselectrofracturing in my application 41,418, supra, or where it isdesired to form a coke deposit in the vicinity of the borehole.

Therefore, an object of the instant invention is to provide methods ofsubsurface electrification where the benefits of subsurface electricaltreatments of all types may be obtained in single well installations.

Another object of the invention is to provide methods of providingsubsurface electrical and electrification treatment in single wellboreinstallations including permeability increase, wellbore fracturing,wellbore coking, channel carbonization, and the like.

Another object of the invention is to provide methods of subsurfaceelectrification which make available the benefits of same at a muchlesser cost in well completions, drilling, apparatus and equipment.

Another object of the invention is to provide new methods of increasinghorizon permeability, penetrating an earth formation by electrolinkingand electrochannel carbonization, preparation for the use of fluidproduction aids such as underground combustion, water and gas drive andaccomplishing electrical fracturing.

Another object of the invention is to provide methods of subsurfaceelectrical treatment which obviate the need of carefully spaced adjacentwellbores penetrating to the single horizon or formation to be treated.

Another object of the invention is to provide subsurface electricaltreatment processes which may be employed in a variety of ways andutilizing a variety of apparatus.

Yet another object of the invention is to provide methods of subsurfaceelectrical treatment and electrification which will make available suchprocesses for a much broader spectrum of purposes, and a broaderclassification of horizons, earth formations, oil fields and the like,particularly with relation to inaccessible terrains and the like.

Yet another object of the invention is to provide methods of improvingproduction conditions at a single wellbore by a variety of electricalprocesses which do not require the existence of an adjacent secondwellbore linked into the electrical circuit.

Yet another object of the invention is to provide such single wellsubsurface electrification processes which do not require as muchmaintenance, require much less equipment, and wherein all elements ofthe apparatus are generally closer to hand for maintenance, repair andmonitoring than in a multiple Well application or completion system.

Other and further objects of the invention will appear in the coure ofthe following description thereof.

In the drawings, which form a part of the instant speci fication and areto be used in conjunction therewith, embodiments of the invention areshown and, in the various views, like numerals are employed to indicatelike parts.

FIG. 1 is a cross-sectional view through an earth formation or horizoncontaining an oil sand or horizon, a

single wellbore drilled into the oil sand and apparatus adapted topractice the instant process schematically shown therein.

FIG. 2 is a fragmentary view of the earth formation of FIG. 1 showingapparatus installed in the same wellbore, adapted to fiuid fracture thesand or horizon after such fracture.

FIG. 3 is a schematic plan view of the oil sand in FIG. 1 after practiceof a first stage of one modification of the inventive process.

FIG. 4 is a cross-sectional view of the earth formation of FIG. 1illustrating a first type of surface ground adaptable for use in theinstant process.

FIG. 5 is a view similar to that of FIG. 4 illustrating a second type ofsurface ground usable in the instant process.

FIG. 6 is a view similar to those of FIGS. 4 and 5 illustrating a thirdtype of surface ground usable in the instant process.

FIG. 7 is a view similar to those of FIGS. 4-6, inclusive, showing afourth type of surface" ground usable in the instant process.

FIG. 8 is a view taken along the line 88 of FIG. 4 in the direction ofthe arrows.

FIG. 9 is a view taken along the line 9-9 of FIG. 5 in the direction ofthe arrows.

FIG. 10 is a view taken along the line 1010 of FIG. 6 in the directionof the arrows.

FIG. 1 completion Referring first to FIG. 1, therein is shown a typicalapplication of apparatus to practice the inventive method in an oilhorizon. The showing is to some extent schematic, but involves actualapparatus employed to practice the invention, with the exception of theschematic designation of the surface ground which will be amplified bylater reference to FIGS. 47, inclusive. At 11) is designated the groundlevel of the earth formation 11 which overlies oil formation or horizon12 and overburden 13 of nonpermeable rock, shale, etc. therebyfurnishing a reservoir for the hydrocarbon containing oil horizon 12. At14 is shown a wellbore which is drilled through earth formation 11 andoverburden 13 into and optionally through or to the bottom of oil sand12. The criterion of extension of the wellbore 14 into sand or horizon12 is to provide sufficient wellbore face within the horizon to permitthe flowing of an adequate or desired quantity of gas or liquid into thehorizon at a desired level if fluid fracturing is desired to be employedand also sulficient depth to permit the spacing of and positioning ofthe subsurface wellbore electrode or electrodes used in the instantprocess at a desired level therein. The upper portion of wellbore 14down to horizon 12 may be of greater diameter than the wellbore in thehorizon or the same diameter, as desired. If the casing of the well isto be inserted in wellbore 14 before drilling is continued into thesand, the hole into the sand may be rat-holed within the larger diameterwellbore and cas- Suitable pipe or casing 15 is run from the surface atleast to the top of oil horizon 12 and preferably slightly thereinto. Ifthere are any earth formation Zones above the oil horizon which need tobe sealed to avoid leakage of formation fluids into wellbore, these maybe sealed or cemented in conventional manner and, if there is anyproblem of leakage of horizon fluids into permeable zones above theformation, the casing 15 may be sealed as required as at 15a to avoidsuch leakage and fluid loss. Casing 15 preferably extends continuouslyfrom horizon 12 to the surface and has input flowline or pipe 16 withvalve 17 thereon connected thereto adjacent well end 15!). Suitable aircompressors or fluid pumps of conventional sort (not shown) may beprovided on line 16. Casing 15 may be, particularly in the vicinity ofhorizon 12, of electrically insulating material or have an electricallyinsulating sheath 18 of tape or other material wrapper I or formedtherearound such as a layer of electrically insulating plastic on theoutside thereof.

A hollow, electricity-conducting metal (steel) tubing 19 extendsdownwardly through wellhead 151) into horizon 12 to a desired depth.Insulator 20 electrically insulates tubing 19 from casing wellhead 15b,while electrically insulating centralizers 21 of any suitable materialsuch as lastic, rubber or ceramic are periodically spaced and positionedalong the length of tubing 19 so as to prevent any electricityconducting contact between tubing 19 and casing 15 and also to evenlyspace the former from the latter. Centralizers 21 must be particularlyspaced near the tubing joints, as well. Tubing 19 preferably has anelectrically insulating sheath 22 of plastic or insulating tapesurrounding its entire length within casing 15, and in any case, verypreferably has such insulation sheath from its lower end in the horizonto a level above any contemplated liquid level in the wellbore 14.Flowline 23 with valve 24 controlling flow therethrough and having pump25 of conventional type connected therewith is taken from the top oftubing 19 above wellhead 15!).

A suitable form of electrode for applying current in the wellbore orformation in the instant processes is shown connected to the lower endof tubing 19 and contacting the wellbore wall within the oil sand at adesired level. Curved steel spring 26 having horizon contacting point 27is connected at its upper end to tubing 19. A brace 28 of steel, whichmay be insulated or of a dielectric substance, particularly on theopposite side thereof from electrode 26, preferably extends downwardlyat least a substantial portion of the vertical distance of extension ofelectrode 26 and carries pin 29 extending through an opening (not shown)in electrode 26 whereby coil spring 3!), backed by brace 28 may forceelectrode 26 outwardly toward the wellbore wall. Coil spring 30 may beso constructed as to be compressed during electrode insertion in thewellbore and released thereafter in the horizon.

Electrical connection 31 to the upper end of tubing 19 connects cable orwire conductor 32 of conventional sort to a source of electrical owerschematically shown at 33. The latter is preferably but not necessarilyan alternate current source of sufficient current capacity and voltagelevel for the process to be practiced. A DC. source is also acceptable.Suitable generators and transformers of conventional type or connectionto an electrical power line or other source of power of the desiredmagnitude and intensity may be employed. Connected to the other side ofthe electrical power source by cable or wire conductor 34 is a surfaceground schematically designated at in FIG. 1, which may be of the typeshown in any one of FIGS. 4-7, inclusive, or other suitable ground forthe purposes to be described.

The purpose of the described apparatus and well completion in wellbore14 and associated therewith is to provide a path for current flow fromthe source of power 33 through conductors 32 and 34 to tubing 19 andfrom thence to electrode 26 from whence the current is to be passed,without arcing between the tubing and easing or electrode and easing,through the earth formation and horizon 12 to the ground electrodeconnection 35 outside strata 12. The presence of any liquids or vapors1n casing 15 which might tend to cause a short or an arc may benullified, as previously mentioned, by suitable sheathing and insulationof the various conductors and casings along their lengths to avoid anyshort circuits or arcs. Additionally, apparatus as shown in my application Serial No. 94,375, filed March 8, 1961, now abancloned forPotential Equalization Between Ground Electrode and Casing to minimize acurrent arcing between tubing and casing may be installed.Metal-to-metal contact between the tubing 19 and casing 15 cannot bepermitted.

In place of a conventional source of electrical power such as an AC. orDC. generating system, the source of electrical power may constitute orcomprise any one of the impulse discharge systems disclosed in myapplication Serial No. 41,418, supra.

Types of surface ground electrodes The varying forms of surface groundelectrodes shown in FIGS. 4-7, inclusive, will be now described. In eachcase, the ground surface will be designated as and the subsurface earthlayer thereto designated 11.

FIG. 4 shows the insulated conductor 34 coming from the power source,and passing to and electrically connecting with an undergroundconductive metal piece 38, typically a steel or copper beam or bar,having a length completely buried in the earth. More than one linked inparallel may be employed. If desired, and in place of the beam or bar38, a hollow cylindrical steel pipe could be buried in the earthextending vertically or horizontally as desired. It is desirable to haveat least a portion of the surface ground electrode or array thereofexposed at the surface whereby they can be observed to see whether steamor water vapor is being produced thereat in practice of the process, inwhich case it may be inferred that the resistance is rising at same anda greater electrode surface is required.

FIG. 5 shows a single rod-type electrode 39 connected to insulatedconductor 34. Steel rod 39 extends vertical- 1y into the earth asuflicient distance to handle current densities of the process involvedwithout sufliciently heating the earth formation therearound andsubstantially raising the resistance thereat. In all cases, the surfaceground electrode contact with the earth will be considerably greater inarea than the electrode contact in the earth formation or horizon to betreated. If the given surface ground electrode can handle the currentdensities over the period of time of operation of the process withoutitself heating to any appreciable degree, it will not heat the groundtherearound and raise the resistance therein.

FIG. 6 shows a plurality of steel bar electrodes 40, 41 and 42 connectedat a common juncture 43 to conductor 34. This installation has thevirtue of requiring lesser depth of insertion to achieve a given resultthan the installations of FIGS. 4 and 5.

FIG. 7 shows yet another surface ground electrode installation which hasproved satisfactory in the instant process. In many earth formations,old wells, often completely cased, remain in the field to greater orlesser depths than the wellbore carrying the electrode to the horizon orsand to be treated. In the case of casings running through the sand tobe treated, this sort of surface ground connection has been foundundesirable for the reason that the vertical extent of the oppositeelectrode to the producing electrode in the sand is so great that thecurrent diffusion is not channeled as desired. In-

stallation of a conventional dual electrode circuit is easier and moresuccessful. However, in lesser depth (than the horizon to be treated)pipes or casings set in the ground in the manner shown in FIG. 7 thesurface ground effect is most often eminently satisfactory. In anopen-ended casing 44 of the type shown, particularly when the interiorof the casing is somewhat filled with Water or other liquid 45, oftenconsiderable electrically generated heat loads may be applied to thecasing without seriously disturbing the desired current activities in.when conductive surface casing is not available it is often muchcheaper to employ the other forms shown.

The shape and location of groun is not significant. However, it has tocarry enough power without reaching 212 F. At this temperature, theground is lost.

Process general description The remarks on the art and applicationslisted in the preamble indicate that it is known to be feasible to (1)electrically cur-rent flow-link two wellbores embedded in the same oilsand whereby to increase permeability of the oil sand or coal seamtherebetween, (2) actually physically link two wellbores in the sameearth strata by electrocarbonizing .a channel therebetween, (3)electrocarbonize the vicinity of the wellbores of two linked electrodesin a single earth strata, (4) electrically physically fracture thewellbore walls in two electrodes in the same strata and the like, and(5) utilize preliminary physical (fluid) frac .turing to aid subsurfaceelectrification in paired boreholes.

I have discovered that I can accomplish permeability increase in,physical channeling through, wellbore car- 'bonization in and physicalfracturing (electrical) at the wellbore of a single well into the stratato be treated in the instant process without requiring another electrodein a laterally spaced well in the same strata. I can also combine insingle wellbore practice various processes such as electrolinkingfollowed by electrocarbonization, physical fracturing by electricalmeans followed by electrolinking and electrocarbonization, etc.

The unique apparatus arrangement and provision of my instant process isto provide a surface ground, that is, ground means suitably varied inthe earth strata above the horizon to be treated (and most convenientlyat, com- .municating with, or closely adjacent to the surface) whichwill handle the current transfers to be employed in the process withoutheating sufiiciently in the ground installation to dry out the groundwater and electrolyte-carrying fluids therearound in such manner as tosubstantially raise the resistance (electrical) in the surroundingterrain. I accomplish this by providing surface ground electrodes ofsufiicient number and/or length and area to handle the electricalcurrent and current densities in the operating system Without suchheating. As the resistance characteristics of any given formation,indeed, any given level of a formation may vary greatly according to theelectrolyte or mineral content therein, it is essentially impossible, asit has been in the double well art systems to precisely predictbeforehand what the precise electrical characteristics of the systemwill be.

A further variable in selecting surface ground electrodes depends uponthe type of process to be carried out. Thus, if it is merely desired tocoke a wellbore, a conductor may be extended a short distance from thewellbore with a suitable pattern of electrodes distributed in the earthconcentrically around the wellbore or concentrated on one side thereofif it is desired to coke particularly in one direction. In thiscompletion, arcing from the top of the tubing is the particular concernso that the electrode must be spaced away from the wellbore suflicientlyto avoid this contingency.

In any case, observation of the ground electrodes as to whether they aresteaming off water vapor from their vicinity or heating up will soondemonstrate whether or not the current carrying capacity of a givenground electrode is adequate for the current densities and patterns being employed in the process.

When it is desired that the electrification extend a greater distance inone direct-ion than the other, then the ground electrode or electrodesof my system are moved further outwardly from the wellbore whereby thecurrent will tend to take a more lateral direction rather than animmediate vertical upturn as would be the case in wellbore coking.Gene-rally, any oil sand will offer a relatively greater permeability toelectrical current passage (due to connate water therein acting aselectrolyte) than the nonoil-containing earth strata thereabove orbelow.

This permeability also contributes to the desired lateralelectrification effects. I have discovered that it is almost an axiom ofpractice that, to achieve a surface-horizon linkage in the mannerdescribed in this application, as opposed to the creation of ahorizon-horizon linkage as in my previous applications and patent, agreater electrical current is required to achieve a comparable effect atthe electrode in the wellbore penetrating the horizon. However, theother advantages of the instant process in most casesfar out weigh thisparticular drawback.

Where, as in FIG. 1, the surface electrode or electrode array is moved aconsiderable lateral distance from the wellbore in a directional manner,the passage of current is generally as seen in FIG. 3 with the greatestcurrent density present at and permeability increase and carbonizationeffects first achieved closely adjacent the well-bore on the side of theelectrode and ground connection. The current flow distributes itselfapproximately in the fan shape shown before moving upwardly out of thehorizon toward the ground electrode.

When it is desired to increase permeability strongly on one side of awellbore, or carbonize and channel in a single direction from thewellbore, or prepare for a sweep injection in a single direction, theapparatus and process of FIG. 1 is that employed and is as illustrated.Another use of the FIG. 1 completion and process is to link twowellbores in a single seam as in the manner of my previous patent andapplications, but where permeability conditions are such and thedistance apart of the wellbores is such that a stable directionallinkage is very difficult or impossible to accomplish. In such case, thedesired single strata interlinkage between the two distant wellbores maybe obtained by first surface linking as immediately above described andshown in FIG. 1 from each wellbore in the direction of the other toestablish a definite trend of permeability in that direction, thenremoving the surface electrodes and linking paired electrodes in thesame seam or horizon, one to the other, in the manner of my patent.

Process variations I disclose, without limitation, the use of the singlewellbore electrode with surface ground electrode technique and apparatusin the following processes:

1) Circumferential wellbore carbonization or coking employing aconcentric pattern of surface ground electrodes around the wellbore ofthe type shown in the figures, particularly FIGS. and 6.

(2) A process of wellbore carbonization with similar results to 1),supra, but biased to one side of the well by the lateral placement ofthe surface ground electrode or electrode array, rather than having aconcentric ground electrode as in the manner of (1), supra. This is anarrangement identical to that of FIG. 1, but with the surface groundelectrode or array not as far laterally displaced as in FIG. 1, indeed,preferably not any further laterally displaced than required to obviatearcing between the casing and the surface ground electrodes under thecurrent densities employed. 1

(3) Step linking or subsurface electrification involving one or twowellbores. In the case of one wellbore, an initial subsurfaceelectrification may be undertaken with a laterally displaced surfaceground electrode whereby to cause electrical effects to extend laterallyto a certain distance in the horizon. Following this, the electrode maybe yet further displaced in the same general radial direction from thewellbore whereby the horizon electrification effect may be extendedalong the line or trend of permeability increase carbonization, etc.already started. In this manner, it is possible to electrically treatand create increased permeability effects, carbonization, wellborecharring effects, etc. in greater extent and to a greater distance in asingle direction than are able to be created when the surface groundelectrode is initially moved out to the further distance originally.

As a variation on this process, two rather widely separated wells may bemore efficiently and effectively electrolinked and electrocarbonizedtherebetween if intermediate electrification steps are taken from eachwellbore toward the other by at least one step link utilizing a surfaceground electrode as seen in FIG. 1.

(4) This process also contemplates the beneficial use of electrolytic orelectricity-conducting particles, such as copper, steel filings, etc.,in a single wellbore installation in the following manner. As a firststep, a hydrofracture may be made in the wellbore prior to any horizonelectrical treatment or after processes (1) or (2). The hydrofractureutilizing fluid carrying electrolytic particles is then followed bylateral electrification as in FIG. 1. The current flow is aided by theuse of the conducting particles injected in the fracturing process. Suchparticles enable a greater concentric of current flow in the horizon (asdesired) for a greater time and a greater lateral exten sion thanwithout same.

As a further improvement involving the step of wellbore coking Idisclose first hydrofracing in the manner of FIG. 2 with the injectionof conductive particles, then utilizing a single well electrificationcircuit as seen in FIG. 8 with the horizon contacting electrodespositioned at or closely adjacent the fractures whereby the current iscarried laterally by the conductive particles a more considerabledistance before being displaced upwardly toward the casing. Either ofthe processes of FIG. 1 or FIG. 8 may he used after the fracturing step.This procedure may be also employed with a plurality of concentricallyspaced surface ground electrodes as described elsewhere in theapplication to obtain a wellbore coking effect extending yet furtherlaterally. In all instances, the primary fracture with conductiveparticles in the fluid, is preferably made at the greatest verticaldisplacement from the casing as possible.

(5) A fifth form of the instant process comprises the application of theinstant process as an improvement over my Serial No. 41,418, supra,wherein electric shock physical fracturing of the wellbore is achievedwith the use of but the single wellbore to be fractured, a surfaceground electrode of the types described and the electricity sources ofSerial No. 41,418. Utilizing the apparatus of FIG. 8, the casing alonemay be used as the surface ground, but the arcing problem is moresevere. However, this gives a more concentric fracture, if such isdesired. Concentrically placed surface ground electrodes applied farenough away to avoid surface arcing give much better control. In thisprocess, larger area surface ground electrodes are required. In theevent that the fracturing is desired to be directional as in FIG. 1, theground electrode or array of same may be laterally displaced aconsiderable distance whereby to draw the fracturing force in the samedirection.

Thus it is seen that I have provided processes of and apparatus forcarrying out all of the noted subsurface electrification processescontemplated by the art wherein the art used a plurality of wellboresand a plurality of electrodes in the same horizon yet have limited thenecessary apparatus to a single well bore penetrating the horizon withan additional ground electrode. I have improved and modified theseprocesses and added new processes with new results. The tremendoussaving and economy of equipment, drilling expenses, etc. will makepossible for more general application of electrical subsurface treatmentas its undesirable benefits can be achieved at a relatively minimumcost. Additionally it is well-known that unforeseen and unpredictedphenomena can take place in wellbore fluids, the geology and geographicearth formation, the type of mineral fuel or hydrocarbon horizon beingtreated, etc. By focusing the electrical efforts in a single wellboreand in a single, easily observable surface ground electrode or electrodearray, adjustments and changes may be undertaken far more quickly andwith far less expense and trouble and any difficulties isolated andcompensated for far more easily and quickly than in a multiple wellboresetup as known to the art.

From the foregoing it will be seen that this invention is one welladapted to attain all of the ends and objects hereinabove set forthtogether with other advantages which are obvious and which are inherentto the process.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the scope of theclaims.

As many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth or shown in the accompanying drawings is to beinterpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim:

1. A process of aiding production of oil from a subsurface oil horizoncomprising the steps of drilling a wellbore into an oil horizon in anearth formation, establishing an electrode in said oil horizon inelectrical current conducting contact with said wellbore wall,establishing at least one other second electrode in said earth formationin high electrical current conducting surface ground contact therewithoutside of, above and laterally displaced from said first wellbore,connecting a high energy source of electrical current to saidelectrodes, flowing a suflicient quantity of electrical current betweensaid electrodes in said earth formation as to create and establish azone of increased fluid flow permeability in said oil horizon extendingoutwardly and laterally from said first electrode toward said lateralposition of said second electrode, said second elect-rode of suchphysical size and characteristics and so inserted in said surface groundrelationship in said earth formation as not to substantially heat theearth formation receiving same at the current densities applied, thenceasing said current flow, then further laterally displacing said secondelectrode away from said electrode along the line of said fluid flowpermeability increase, then again establishing said second electrode asa surface ground and, following the latter, flowing a second suflicientquantity of high energy electrical current between the said electrodesin said earth formation whereby to establish a further laterallyextending second zone of increased fluid flow permeability in saidhorizon extending towardthe lateral position of said second electrode,the second electrode in its second position in such physical andelectrical conducting character and so positioned in said earthformation as a surface ground as to not substantially heat the earthformation receiving same as to raise the resistance thereat at thecurrent densities applied.

2. A process of aiding production of oil from a subsurface oil horizoncomprising the steps of drilling a wellbore into an oil horizon in anearth formation, establishing a first electrode in said oil horizon inhigh electrical current conducting contact with the said Well bore Wallwithin said horizon, fracturing the oil horizon in said wellboresubsequent to drilling the wellbore into the oil horizon and prior toelectrical treatment whereby to establish an outwardly extending radialfracture zone in said horizon, establishing at least one other secondelectrode in high electrical current conducting surface ground contactwith said earth formation outside of, above said oil horizontal andlaterally displaced from said first wellbore, connecting a high energysource of electrical current between said electrodes, flowing asufficient quantity of electrical current between said electrodes insaid earth formation as to create and establish a zone of increasedfluid flow permeability within said oil horizon, said zone extendinglaterally from said first electrode within said horizon toward thelateral position of said second electrode with respect thereto, saidsecond electrode of such electrical conducting size and character and soinserted in said earth formation as to not substantially heat the earthformation receiving same at the current densities applied, whereby tosubstantially raise the resistance thereat.

3. A process as in claim 2 including the step of forcing electricallyconductive particles into said fracture prior to any electrification.

References Cited by the Examiner UNITED STATES PATENTS 2,217,857 10/40Byck 204-180 2,625,374 1/53 Neuman --5O 2,795,279 6/57 Sarapuu 166112,799,641 7/57 Bell.

2,801,090 7/57 Hoyer et a1 16639 X 2,806,818 9/57 Howard 204 2,818,11812/57 Dixon 166-11 3,106,244 10/63 Parker 16611 BENJAMIN HERSH, PrimaryExaminer.

BENJAMIN BENDETT, Examiner.

1. A PROCESS OF AIDING PRODUCTIN OF OIL FROM A SUBSURFACE OIL HORIZONCOMPRISING THE STEPS OF DRILLING A WELLBORE INTO AN OIL HORIZON IN ANEARTH FORMATION, ESTABLISHING AN ELECTRODE IN SAID OIL HORIZON INELECTRICAL CURRENT CONDUCTING CONTACT WITH SAID WELLBORE WALL,ESTABLISHING AT LEAST ONE OTHER SECOND ELECTRODE IN SAID EARTH FORMATIONIN HIGH ELECTRICAL CURRENT CONDUCTING SURFACE GROUND CONTACT THEREWITHOUTSIDE OF, ABOVE AND LATERALLY DISPLACED FROM SAID FIRST WELLBORE,CONNECTING A HIGH ENERGY SOURCE OF ELECTRICAL CURRENT TO SAIDELECTRODES, FLOWING A SUFFICIENT QUANTITY OF ELECTRICAL CURRENT BETWEENSAID ELECTRODES IN SAID EARTH FORMATION AS TO CREATE AND ESTABLISH AZONE OF INCREASED FLUID FLOW PERMEABILITY IN SAID OIL HORIZON EXTENDINGOUTWARDLY AND LATERALLY FROM SAID FIRST ELECTRODE TOWARD SAID LATERALPOSITION OF SAID SECOND ELECTRODE, SAID SECOND ELECTRODE OF SUCHPHYSICAL SIZE AND CHARACTERISTICS AND SO INSERTED IN SAID SURFACE GROUNDRELATIONSHIP IN SAID EARTH FORMATION AS NOT TO SUBSTANTIALLY HEAT THEEARTH FORMATION RECEIVING SAME AT THE CURRENT DENSITIES APPLIED, THENCEASING SAID CURRENT FLOW, THEN FURTHER LATERALLY DISPLACING SAID SECONDELECTRODE AWAY FROM SAID ELECTRODE ALONG THE LINE OF SAID FLUID FLOWPERMEABILITY INCREASE, THEN AGAIN ESTABLISHING SAID SECOND ELECTRODE ASA SURFACE GROUND AND, FOLLOWING THE LATTER, FLOWING A SECOND SUFFICIENTQUANTITY OF HIGH ENERGY ELECTRICAL CURRENT BETWEEN THE SAID ELECTRODESIN SAID EARTH FORMATION WHEREBY TO ESTABLISH A FURTHER LATERALLYEXTENDING SECOND ZONE OF INCREASED FLUID FLOW PERMEABILITY IN SAIDHORIZON EXTENDING TOWARD THE LATERAL POSITION OF SAID SECOND ELECTRODE,THE SECOND ELECTRODE IN ITS SECOND POSITION IN SUCH PHYSICAL ANDELECTRICAL CONDUCTING CHARACTER AND SO POSITIONED IN SAID EATH FORMATIONAS A SURFACE GROUND AS TO NOT SUBSTANTIALLY HEAT THE EARTH FORMATIONRECEIVING SAMD AS TO RAISE THE RESISTANCE THEREAT AT THE CURRENTDENSITIES APPLIED.